1. Field of the Invention
The present invention relates generally to track-jump (seek) controlling apparatuses and methods that control track-jump operations with respect to a disk attached to a disk player, and particularly to a track-jump controlling apparatus and method which is applicable to a disk player capable of playing different types of disks and which are designed to control track-jump operations such that an optimum track-jump operation is selected for each type of disk.
2. Description of Related Art
Disk players that can play a disk such as a DVD, for example, change the reproducing position of the disk by a track-jump (seek) operation through which their pickup is moved to a remote, desired track. When the pickup is moved from a current reproducing position to a seek target position, the number of tracks crossed by the pickup, or track crossings, is counted to obtain the exact distance moved by the pickup. In the case of DVD-ROMs, for example, the DPD (Differential Phase Detection) method is used, which is based on diagonal sum signals obtained from light intensity patterns detected by a quad photodetector. In this method, a phase difference between the relevant diagonal sum signals is detected to obtain a phase difference signal, and zero crossing points in such phase difference signals are detected to count track crossings.
By the way, latest versions of disks complying with DVD formats include, in addition to the above-mentioned DVD-ROMs as read-only memory devices, DVD-Rs (DVD-Recordable or DVD Write Once) and DVD-RWs (DVD-Rewirtable) as recordable devices, and the latter devices are now gaining in popularity. Thus, it is desirable to manufacture a DVD disk player that can play all types of DVD disks independently of their data formats.
However, such a disk player may have difficulty performing accurate track-jumping (seeking) with respect to these different types of DVD disks in some cases. For example, in a DVD having unrecorded areas where no data is recorded, no pits are formed in such unrecorded areas. Since DPD tracking error signals based on the DPD method require the presence of pits to detect phase differences, the use of the DPD tracking error signals would cause trouble in counting track crossings for the DVD. Further, a DVD-RW has a format requiring that an embossed pit array be included in its control data zone, and the pits formed in the embossed pit array are not so deep that DPD tracking error signals cannot be detected at sufficient levels. That is, the problem is that a track-jump operation using DPD tracking error signals is not applicable commonly to both DVD-ROMs and DVD-RWs.
The present invention has been made in view of this problem, and an object thereof is, therefore, to provide a track-jump controlling apparatus and method that can perform highly reliable track-jumping while accurately counting track crossings at all times, in an optical system that can accommodate different types of disks.
The above object of the present invention can be achieved by a track-jump controlling apparatus of the present invention for controlling a track-jump operation by moving a pickup in a radial direction of a disk, which is one of different types of disks. The apparatus is provided with: a first generating device for generating a differential phase detection (DPD) tracking error signal based on photodetection signals from said pickup; a second generating device for generating a push-pull signal based on said photodetection signals from said pickup; a signal selecting device for selecting one of said DPD tracking error signal and said push-pull signal as a signal for use in said track-jump operation according to a state of said disk before said seek operation is performed; and a track-jump operation device for performing said track-jump operation from a current reproducing position to a seek target position over said disk, while counting track crossings using said signal selected by said signal selecting device.
According to the present invention, the DPD tracking error signal and the push-pull signal are generated based on the photodetection signals from the pickup during a track-jump operation with respect to a disk, and one of the two signals is selected according to the state of the disk, whereby the selected signal is used to count track crossings to perform the track-jump operation from the current reproducing position to the seek target position. That is, the signal used for track-jumping (seeking) is optimized for each type of disk, whereby the number of tracks can be counted accurately at all times, and hence a highly reliable seek operation can be realized. In addition, even when a seek operation is performed in an optical system that can accommodate different types of disks, reliability in seeking can be improved while keeping accurate counting of track crossings.
In one aspect of the present invention, said disk is one that can only read data recorded in advance or one that can both record data and read recorded data, said signal selecting device determines whether an area where a degree of modulation of said photodetection signals is small is present, and selects said push-pull signal when it is determined that said area where a degree of modulation of said photodetection signals is small is present between said current reproducing position and said seek target position.
According to this aspect of the present invention, if a track-jump operation over said area where a degree of modulation of said photodetection signals is small is performed, Said push-pull signal is selected. Therefore, even if the DPD tracking error signal is unavailable because of the track-jump operation over said area such as an area where no pit is formed on a recording track, accurate counting of track crossings is executed.
In another aspect of the present invention, the apparatus is further provided with a wobble signal detecting device for detecting a wobble signal from said photodetection signals, said wobble signal based on wobbled recorded tracks of said disk. In addition, said signal selecting device selects said push-pull signal when said wobble signal has been detected by said wobble signal detecting device.
According to this aspect of the present invention, a wobble signal extractable from wobbled recorded tracks of a rewritable disk is utilized. When the wobble signal is detected from a predetermined area of the disk during seeking, push-pull signals are used. Hence, even when DPD tracking error signals obtained from the predetermined area of the disk having wobbled recorded tracks are not at proper levels, track crossings can be counted accurately by using the push-pull signals.
In further aspect of the present invention, said disk is a DVD-ROM that can only read data recorded in advance or a DVD-RW that can write data repetitively. Said DVD-RW includes a control data zone having an embossed pit array formed therein, said embossed pit array corresponding to predetermined control data. Further, said track-jump controlling device controls said track-jump operation such that said pickup passes over said control data zone.
According to this aspect of the present invention, when a track jump operation involving passage over a control data zone is to be performed in a DVD-RW, and if a wobble signal is detected from a predetermined area, then the push-pull signal is selected. Hence, when the DVD-RW is activated to have the pickup passed over an embossed pit array formed in its control data zone, an improper seek operation due to a pit having a small depth can be avoided.
The above object of the present invention can be achieved by a track-jump controlling method of the present invention for controlling a track-jump operation by moving a pickup in a radial direction of a disk, which is one of different types of disks. The method is provided with the processes of: a first generating process of generating a DPD tracking error signal based on photodetection signals from said pickup;
a second generating process of generating a push-pull signal based on said photodetection signals from said pickup; a selecting process of selecting one of said DPD tracking error signal and said push-pull signal as a signal for use in said seek operation, according to a state of said disk before said track-jump operation is performed; and a controlling process of controlling said track-jump operation such that said pickup moves from a current reproducing position to a seek target position over said disk, while counting track crossings using said selected signal.
According to the present invention, the DPD tracking error signal and the push-pull signal are generated based on the photodetection signals from the pickup during a track-jump operation with respect to a disk, and one of the two signals is selected according to the state of the disk, whereby the selected signal is used to count track crossings to perform the track-jump operation from the current reproducing position to the seek target position. That is, the signal used for track-jumping (seeking) is optimized for each type of disk, whereby the number of tracks can be counted accurately at all times, and hence a highly reliable seek operation can be realized. In addition, even when a seek operation is performed in an optical system that can accommodate different types of disks, reliability in seeking can be improved while keeping accurate counting of track crossings.
In one aspect of the present invention, said disk is one that can only read data recorded in advance or one that can both record data and read recorded data, the method is further provided with a determining process of determining whether an area where a degree of modulation of said photodetection signals is small is present, and said controlling process controls said track-jump operation by selecting said push-pull signal when it is determined that said area where a degree of modulation of said photodetection signals is small is present between said current reproducing position and said seek target position.
According to this aspect of the present invention, if a track-jump operation over said area where a degree of modulation of said photodetection signals is small is performed, Said push-pull signal is selected. Therefore, even if the DPD tracking error signal is unavailable because of the track-jump operation over said area such as an area where no pit is formed on a recording track, accurate counting of track crossings is executed.
In another aspect of the present invention, the method is further provided with a detecting process of detecting, from said photodetection signals, a wobble signal based on wobbled recorded tracks of said disk, wherein said controlling process controls said track-jump operation by selecting said push-pull signal when said wobble signal has been detected.
According to this aspect of the present invention, a wobble signal extractable from wobbled recorded tracks of a rewritable disk is utilized. When the wobble signal is detected from a predetermined area of the disk during seeking, push-pull signals are used. Hence, even when DPD tracking error signals obtained from the predetermined area of the disk having wobbled recorded tracks are not at proper levels, track crossings can be counted accurately by using the push-pull signals.